1. Field of the Invention
The present invention relates to a control method in the feeding of plate shaped workpieces to a work station, comprising feeding of the workpiece to a control station at which control station it is controlled that the desired number of workpieces are at the control station before moving the workpiece to the work station. The invention also relates to a control station in connection with the feeding of workpieces to a work station, comprising a receiving section, a fixing structure arranged to position/fix the receiving section and at least one detecting means in communication with a control unit and arranged to detect the number of workpieces on top of the receiving section.
2. Prior Art
Automated production lines have been well known for long. In some production lines, such as pressing lines for the production of details of shaped plate, for example in the production of body details in motor-car production, there is a particular problem in connection with automated feeding. In the following, said problem will be described in connection with such a pressing line, but it is realized that the invention is not limited to the use of such pressing lines. A pressing line consists of a plurality of different pressing stations into which a predetermined plate detail is introduced at one end and is then successively pressed to the desired shape in the different presses in the pressing line. It is of great importance for the profitability of such production that the machine availability is high at the machines and that the processing time is as short as possible. One occurring cause of stoppage in such a pressing line is that more than one plate is accidentally fed into the pressing line, so called double feeding. Double feeding of plates will namely result in problems since the pressing line is designed/dimensioned to handle a single plate at the time. The consequences of double feeding can be that one or in worst case a plurality of the presses and/or the tools in the line break(s) down. In either case, such double feeding most often results in non desired stoppage.
With the purpose of eliminating double feeding, there is a control station at the feeding station for a pressing line, the object of which is to eliminate double feeding. Traditionally, such a control station has been manned for the performing of said control and to make sure that not more than a single plate is feed into the line at the time. For several reasons, such as economical reasons, there is however a strive to eliminate manning at a control station. Accordingly, there is today many types of known arrangements to achieve automated control. The most common arrangements make use of either inductive sensors and/or optical sensors. Another type of principle arrangement to avoid double weighing is known from DE 4322963 and DE 10027144. This known principle uses lifting mechanisms with suction cups and the weighing is performed in connection with the lifting/moving. Such known arrangements will however not work completely satisfactory in all situations and are relatively expensive.